Tire for automatic two-wheeled vehicle

Abstract

The present application provides a tire for an automatic two-wheeled vehicle that can exhibit excellent cornering performance even when the centrifugal force is small, such as from a straight-ahead state to a slow cornering state. The tire for an automatic two-wheeled vehicle includes a carcass and a tread reinforcement layer disposed on the outer side in the tire radial direction of the carcass. The tread reinforcement layer includes a belt layer and a crown layer. The belt layer is composed of one inner belt ply disposed adjacent to the carcass with the belt cords arranged at a first angle, and one outer belt ply disposed on the outer side in the tire radial direction of the inner belt ply with the belt cords arranged at a second angle different from the first angle. The crown layer is composed of at least one crown ply. In the tire radial direction, the crown ply is disposed adjacent to the inner belt ply and the outer belt ply between the inner belt ply and the outer belt ply.

Description

TECHNICAL FIELD

[0001] The present application relates to a tire for an automatic two-wheeled vehicle capable of exhibiting excellent cornering performance. BACKGROUND

[0002] In the past, in order to improve cornering performance, a tire for an automatic two-wheeled vehicle including a tread reinforcing layer in a tread portion is known. For example, Patent Document 1 proposes a tire for an automatic two-wheeled vehicle whose tread reinforcing layer is composed of two belt plies disposed on the outer side in the tire radial direction of a carcass and one crown ply disposed on the outer side in the tire radial direction of the two belt plies.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2018-111375

[0004] However, in the tire for an automatic two-wheeled vehicle of Patent Document 1, due to the tightening effect of the two belt plies, a large side force is generated, and when the centrifugal force is small, such as from a straight running state to a slow cornering state, there is a tendency for the force to make the automatic two-wheeled vehicle stand up to increase. Therefore, the tire for an automatic two-wheeled vehicle of Patent Document 1 desires further improvement in cornering performance when the centrifugal force is small. SUMMARY

[0005] The present application was completed in view of the above actual situation, and its main object is to provide a tire for an automatic two-wheeled vehicle capable of exhibiting excellent cornering performance when the centrifugal force is small, such as from a straight running state to a slow cornering state.

[0006] The present application is a tire for an automatic two-wheeled vehicle, characterized by comprising: a carcass that reaches a pair of bead portions from a tread portion via a pair of sidewall portions; and a tread reinforcing layer disposed on the outer side in the tire radial direction of the carcass in the tread portion, the tread reinforcing layer including: a belt layer in which a plurality of belt cords are arranged; and a crown layer in which a plurality of crown cords are arranged, the belt layer being composed of one inner belt ply disposed adjacent to the carcass and one outer belt ply disposed on the outer side in the tire radial direction of the inner belt ply, the belt cords of the inner belt ply being arranged so as to cross the tire circumferential direction at a first angle, the belt cords of the outer belt ply being arranged so as to cross the tire circumferential direction at a second angle different from the first angle, the crown layer being composed of at least one crown ply in which the crown cords are arranged at an angle of 5° or less from the tire circumferential direction, the crown ply being disposed adjacent to the inner belt ply and the outer belt ply between the inner belt ply and the outer belt ply in the tire radial direction.

[0007] In the automatic two-wheeled vehicle tire of the present application, the crown belt ply preferably has an unfolded width that is smaller than the unfolded widths of the inner side belt ply and the outer side belt ply.

[0008] In the automatic two-wheeled vehicle tire of the present application, the crown belt ply preferably has an unfolded width that is 30% to 90% of the unfolded width of the tread.

[0009] In the automatic two-wheeled vehicle tire of the present application, the first angle is preferably 50° to 80°.

[0010] In the automatic two-wheeled vehicle tire of the present application, the second angle is preferably 70° to 90°.

[0011] In the automatic two-wheeled vehicle tire of the present application, the difference between the second angle and the first angle is preferably 10° to 40°.

[0012] In the automatic two-wheeled vehicle tire of the present application, the second angle is preferably larger than the first angle.

[0013] In the automatic two-wheeled vehicle tire of the present application, the tread portion preferably includes a rubber layer disposed on the tire axial outer side of the crown belt ply, the rubber layer being composed of at least one rubber sheet.

[0014] In the automatic two-wheeled vehicle tire of the present application, the tread portion preferably includes a rubber layer disposed on the tire axial outer side of the crown belt ply, the rubber layer being disposed between the inner side belt ply and the outer side belt ply, the distance between the inner side belt ply and the outer side belt ply at the position where the rubber layer is disposed being 0.5 mm to 3.0 mm and being substantially constant.

[0015] In the automatic two-wheeled vehicle tire of the present application, the rubber layer preferably has a complex elastic modulus at 70°C of 500 kPa or more.

[0016] In the automatic two-wheeled vehicle tire of the present application, the crown belt ply is preferably disposed adjacent to the inner side belt ply and the outer side belt ply in the tire radial direction between the inner side belt ply and the outer side belt ply.

[0017] Such an automatic two-wheeled vehicle tire can moderate the pinch effect of the inner side belt ply and the outer side belt ply, and can suppress the generation of excessive cornering power when the centrifugal force is small, such as from a straight running state to a slow turning state. Thus, the automatic two-wheeled vehicle tire of the present application can exhibit excellent cornering performance even when the centrifugal force is small, such as from a straight running state to a slow turning state. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1is a sectional view showing one embodiment of a motorcycle tire of the present application.

[0019] Figure 2 is an expanded view of a tread reinforcing layer.

[0020] Figure 3 is an enlarged sectional view of a tread portion.

[0021] Explanation of Reference Numerals

[0022] 6: carcass; 7: tread reinforcing layer; 8: belt; 8A: inner belt ply; 8B: outer belt ply; 8a: belt cord; 9: crown layer; 9A: crown ply. DETAILED DESCRIPTION

[0023] Hereinafter, one embodiment of the present application will be described in detail based on the drawings.

[0024] Figure 1 is a meridian sectional view of a motorcycle tire 1 (hereinafter, sometimes simply referred to as "tire 1") in a normal state of the present embodiment.

[0025] Here, the "normal state" is a state in which the tire 1 rim is assembled to a normal rim and adjusted to a normal internal pressure and no load. In the present specification, the dimensions of each part of the tire 1 are values measured in the normal state, unless otherwise specified.

[0026] Further, the "normal rim" is a rim determined for each tire in a specification system including the specification to which the tire 1 adheres, for example, "Standard Rim" if JATMA, "Design Rim" if TRA, or "Measuring Rim" if ETRTO.

[0027] Further, the "normal internal pressure" is an air pressure determined for each specification in a specification system including the specification to which the tire 1 adheres, for example, "Maximum Air Pressure" if JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" if TRA, or "INFLATION PRESSURE" if ETRTO.

[0028] As shown in Figure 1 , the tire 1 of the present embodiment includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and a pair of bead portions 4 located inward in the tire radial direction of the sidewall portions 3. For example, a bead core 5 is embedded in each of the pair of bead portions 4.

[0029] The tread surface 2s, which is the outer surface of the tread portion 2, extends in a curved manner, for example, from the tire equator C to the tread end Te, in a convex manner toward the outside in the tire radial direction. In the present embodiment, the position of the tread end Te forms the position of the maximum width of the tire. Such a tire 1 is capable of imparting a large camber angle to turn.

[0030] Here, the tread end Te is the end portion of the tread portion 2 in the tire axial direction. The tire equator C is the center in the tire axial direction between the tread ends Te. Also, the length measured along the tread surface 2s between the tread ends Te is the tread unfolded width TWe.

[0031] The tire 1 of the present embodiment includes a carcass 6 that reaches a pair of bead portions 4 from the tread portion 2 via a pair of side portions 3. The carcass 6 includes, for example, a main portion 6a that straddles the pair of bead cores 5 and a turn-up portion 6b that is connected to the main portion 6a and turns up around the bead cores 5.

[0032] The carcass 6 includes at least one (two in the present embodiment) carcass ply 6A, 6B. The carcass ply 6A, 6B includes, for example, carcass cords arranged at an angle of 75° to 90° with respect to the tire circumferential direction, respectively.

[0033] The tire 1 of the present embodiment includes a tread reinforcement layer 7 disposed outside the tire radial direction of the carcass 6 in the tread portion 2. The tread reinforcement layer 7 of the present embodiment includes a belt layer 8 and a crown layer 9.

[0034] Figure 2 is an unfolded view of the tread reinforcement layer 7 of the present embodiment. As shown in Figure 1 and Figure 2 The belt layer 8 is preferably a belt layer in which a plurality of belt cords 8a are arranged. The crown layer 9 is preferably a crown layer in which a plurality of crown cords 9a are arranged.

[0035] The belt layer 8 of the present embodiment is composed of one inner belt ply 8A disposed adjacent to the carcass 6 and one outer belt ply 8B disposed outside the tire radial direction of the inner belt ply 8A.

[0036] The belt cords 8a of the inner belt ply 8A of the present embodiment are arranged so as to cross the tire circumferential direction at a first angle θ1. The belt cords 8a of the outer belt ply 8B of the present embodiment are arranged so as to cross the tire circumferential direction at a second angle θ2 different from the first angle θ1. Such a belt layer 8 contributes to an increase in the rigidity of the tread portion 2 and generation of a large cornering power by the hoop effect of the inner belt ply 8A and the outer belt ply 8B.

[0037] Here, the turning of the automatic two-wheeled vehicle is performed by tilting the automatic two-wheeled vehicle. At this time, the lateral force generated at the tire 1 is expressed as the sum of the camber lateral force generated due to the tilting of the tire 1 and the cornering power generated due to the slip angle of the tire 1. When the lateral force generated at the tire 1 and the centrifugal force of the automatic two-wheeled vehicle are balanced, the automatic two-wheeled vehicle can turn stably, and it can be said that the turning performance is excellent.

[0038] The centrifugal force of the automatic two-wheeled vehicle becomes smaller, for example, from the straight running state to the slow turning state, and becomes larger from the straight running state to the sharp turning state. Therefore, the tire 1 can suppress the generation of the cornering power from the straight running state to the slow turning state, and increase the cornering power in the sharp turning state, and thus can improve the turning performance from the straight running state to the sharp turning state.

[0039] The tire 1 of the present embodiment can increase the cornering power by the belt 8, and thus the lateral force acting on the tire 1 also becomes larger, and can improve the turning performance when the centrifugal force is large, like in the sharp turning state.

[0040] The crown 9 is composed of at least one (one in the present embodiment) crown ply 9A in which the crown cords 9a are arranged at an angle of 5° or less with respect to the tire circumferential direction. The crown ply 9A of the present embodiment is disposed adjacent to the inner belt ply 8A and the outer belt ply 8B in the tire radial direction between the inner belt ply 8A and the outer belt ply 8B.

[0041] Such a tire 1 can moderate the pinch effect of the inner belt ply 8A and the outer belt ply 8B, and suppress the excessive generation of the cornering power when the centrifugal force is small, like from the straight running state to the slow turning state. Therefore, the tire 1 of the present embodiment can also exhibit excellent turning performance when the centrifugal force is small, like from the straight running state to the slow turning state.

[0042] As a more preferable mode, the development width W1 of the crown ply 9A is smaller than the development width W2 of the inner belt ply 8A and the development width W3 of the outer belt ply 8B. Such a tread reinforcement layer 7 can moderate the pinch effect of the inner belt ply 8A and the outer belt ply 8B from the straight running state to the slow turning state, and can exert the pinch effect in the sharp turning state.

[0043] Therefore, the tire 1 of the present embodiment can suppress the excessive generation of the cornering power from the straight running state to the slow turning state, can generate a larger cornering power in the sharp turning state, and can improve the turning performance from the straight running state to the sharp turning state.

[0044] The development width Wl of the crown belt ply 9A is preferably 30 to 90% of the tread development width TWe. By making the development width Wl of the crown belt ply 9A 30% or more of the tread development width TWe, the crown belt ply 9A can be reliably contained in the ground-contacting portion even in the case where the tread portion 2 is deformed at the time of braking in the straight-ahead state, and the cornering power can be reduced.

[0045] By making the development width Wl of the crown belt ply 9A 90% or less of the tread development width TWe, the pinch effect in the sharp cornering state can be reliably exerted, and the cornering power can be increased. Thus, the tire 1 of the present embodiment can reliably improve the cornering performance from the straight-ahead state to the sharp cornering state.

[0046] The development width W2 of the inner side belt ply 8A is preferably 90 to 100% of the tread development width TWe. The development width W3 of the outer side belt ply 8B is preferably 85 to 95% of the tread development width TWe. The development width W3 of the outer side belt ply 8B of the present embodiment is smaller than the development width W2 of the inner side belt ply 8A. Such a belt 8 can further improve the rigidity of the tread portion 2.

[0047] The first angle θl of the belt cord 8a of the inner side belt ply 8A with respect to the tire circumferential direction is preferably 50 to 80°. By making the first angle θl 50° or more, the pinch effect can be suppressed, a good cornering power can be generated, and the cornering performance can be improved. By making the first angle θl 80° or less, the angle difference can be reliably provided between the belt cord 8a of the inner side belt ply 8A and the belt cord 8a of the outer side belt ply 8B, and the pinch effect can be exerted.

[0048] The second angle θ2 of the belt cord 8a of the outer side belt ply 8B with respect to the tire circumferential direction is preferably 70 to 90°. By making the second angle θ2 70° or more, the pinch effect can be suppressed, a good cornering power can be generated, and the cornering performance can be improved. By making the second angle θ2 90° or less, since the direction of inclination is the same as that of the belt cord 8a of the inner side belt ply 8A, the misplacement at the time of manufacture can be reduced.

[0049] The difference (|θ2-θl|) between the second angle θ2 and the first angle θl is preferably 10 to 40°. By making the difference (|θ2-θl|) 10° or more, the pinch effect based on the inner side belt ply 8A and the outer side belt ply 8B can be exerted. By making the difference (|θ2-θl|) 40° or less, the difference in the magnitude of the cornering power caused by the presence or absence of the crown belt ply 9A can be reduced, and the excessive characteristics at the boundary position of the crown belt ply 9A can be improved.

[0050] The second angle θ2 of the present embodiment is larger than the first angle θ1. In such a belt layer 8, since the angle of the belt cord 8a of the outer belt ply 8B close to the tread surface 2s is larger with respect to the tire circumferential direction, the rigidity of the tread portion 2 can be increased, which contributes to a larger cornering force.

[0051] Figure 3 is an enlarged sectional view of the tread portion 2 of the present embodiment. As shown in Figures 1 to 3 The tread portion 2 of the present embodiment includes a rubber layer 10 disposed on the tire axial outer side of the crown belt ply 9A. It is preferable that the rubber layer 10 be disposed on both sides of the tire axial direction of the crown belt ply 9A. The rubber layer 10 is each composed of at least one (one in the present embodiment) rubber sheet 10A. Here, the state in which the rubber layer 10 composed of the rubber sheet 10A is included indicates a state in which the distance between components disposed across the rubber layer 10 is kept substantially constant. In addition, in the present specification, substantially constant means that the deviation from the average value of the distance is within ±15%.

[0052] Such a tread portion 2 increases the torsional rigidity by the rubber sheet 10A, and can increase the cornering force in a sharp cornering state. Therefore, the tire 1 of the present embodiment can improve the cornering performance in a sharp cornering state. In addition, in the case where the rubber layer 10 is composed of a plurality of rubber sheets 10A, each rubber sheet 10A can be arranged in the tire radial direction, or each rubber sheet 10A can be arranged in the tire axial direction.

[0053] The rubber layer 10 of the present embodiment is disposed between the inner belt ply 8A and the outer belt ply 8B. The distance t between the inner belt ply 8A and the outer belt ply 8B at the position where the rubber layer 10 is disposed is preferably 0.5 to 3.0 mm and substantially constant. Here, the distance t between the inner belt ply 8A and the outer belt ply 8B means the shortest distance between the outer side surface 8As of the inner belt ply 8A and the inner side surface 8Bs of the outer belt ply 8B.

[0054] By the distance t being 0.5 mm or more, the torsional effect can be reliably exerted, and the cornering force in a sharp cornering state can be increased. By the distance t being 3.0 mm or less, the cornering force can be prevented from becoming excessively large, and the excessive characteristics of the region having the crown belt ply 9A can be improved.

[0055] The sum (W1+2xW4) of the development width W4 of the rubber layer 10 on both sides of the present embodiment and the development width W1 of the crown belt ply 9A is smaller than the development width W2 of the inner belt ply 8A and larger than the development width W3 of the outer belt ply 8B. Such a rubber layer 10 can further improve the torsional rigidity of the tread portion 2.

[0056] The complex elastic modulus G* of the rubber layer 10 at 70°C is preferably 500 kPa or more. Such a rubber layer 10 can more reliably exert a torsion effect, and can further increase the side force in a sharp turning state.

[0057] Here, the complex elastic modulus G* of the rubber layer 10 at 70°C is a value measured using a dynamic viscoelasticity measuring device (EPLEXOR series) manufactured by GABO Co. based on the provisions of JIS-K6394 under the following conditions.

[0058] Initial strain: 10%

[0059] Amplitude of dynamic strain: ±1%

[0060] Frequency: 10 Hz

[0061] Deformation mode: Tension

[0062] Measurement temperature: 70°C

[0063] The above describes a particularly preferred embodiment of the present application, but the present application is not limited to the above-described embodiment, and can be modified into various modes and implemented.

[0064]

EXAMPLE

[0065] A tire for an automatic two-wheeled vehicle having the basic configuration of Figure 1 was trial-produced based on the specifications of Table 1. As a comparative example, a tire for an automatic two-wheeled vehicle having a crown layer disposed on the outer side of the tire radius of the belt layer was trial-produced. The trial-produced tires were mounted on the front and rear wheels of a test automatic two-wheeled vehicle, and the slow turning performance from a straight-up state to a slow turning state, the sharp turning performance in a sharp turning state, and the oversteer characteristics from a slow turning state to a sharp turning state were evaluated based on the senses of test drivers. The results are expressed as an index with Comparative Example 1 being 100, and the larger the value, the more excellent the slow turning performance, the sharp turning performance, and the oversteer characteristics. In addition, the main common matters were as follows.

[0066] <Common Matters>

[0067] Front tire size: 120 / 70R17

[0068] Front air pressure: 250 kPa

[0069] Rear tire size: 200 / 60R17

[0070] Rear air pressure: 290 kPa

[0071] Test automatic two-wheeled vehicle: large-sized automatic two-wheeled vehicle

[0072] The results are shown in Table 1.

[0073]

Table 1

[0074]

[0075] As a result of the test, it was confirmed that the tire of the example improved the slow cornering performance while maintaining the sharp cornering performance compared to the comparative example, and was able to exhibit excellent cornering performance even when the centrifugal force was small from the straight running state to the slow cornering state.

Claims

1. A tire for an automatic two-wheeled vehicle, comprising: a carcass reaching a pair of bead portions via a pair of side portions from a tread portion; and a tread reinforcement layer disposed outside the carcass in the tire radial direction in the tread portion, the tread reinforcement layer comprising: a belt arranged with a plurality of belt cords; and a crown layer arranged with a plurality of crown cords, the belt is composed of one inner belt ply disposed adjacent to the carcass and one outer belt ply disposed outside the inner belt ply in the tire radial direction, the belt cords of the inner belt ply are arranged to cross the tire circumferential direction at a first angle, the belt cords of the outer belt ply are arranged to cross the tire circumferential direction at a second angle different from the first angle, the crown layer is composed of at least one crown ply in which the crown cords are arranged at an angle of 5° or less from the tire circumferential direction, the crown ply is disposed adjacent to the inner belt ply and the outer belt ply between the inner belt ply and the outer belt ply in the tire radial direction, the tread portion comprises rubber layers disposed on both sides of the tire axial direction of the crown ply, the tire axial inner end of each of the rubber layers on both sides of the tire axial direction is in contact with the tire axial outer end of the crown ply and is covered by the outer belt ply, the tire axial outer end of each of the rubber layers on both sides of the tire axial direction extends to a position beyond the tire axial outer end of the outer belt ply to the outside of the tire axial direction without being covered by the outer belt ply and without reaching the tire axial outer end of the inner belt ply, the rubber layers are disposed between the inner belt ply and the outer belt ply, and the distance between the inner belt ply and the outer belt ply at the position where the rubber layers are disposed is substantially constant.

2. The tire for an automatic two-wheeled vehicle according to claim 1, wherein the development width of the crown ply is smaller than the development width of the inner belt ply and the development width of the outer belt ply.

3. The tire for an automatic two-wheeled vehicle according to claim 1 or 2, wherein the development width of the crown ply is 30% to 90% of the development width of the tread.

4. The tire for an automatic two-wheeled vehicle according to claim 1 or 2, wherein the first angle is 50° to 80°.

5. The tire for an automatic two-wheeled vehicle according to claim 1 or 2, wherein the second angle is 70° to 90°.

6. The tire for an automatic two-wheeled vehicle according to claim 1 or 2, wherein the difference between the second angle and the first angle is 10° to 40°.

7. The tire for an automatic two-wheeled vehicle according to claim 1 or 2, wherein the second angle is larger than the first angle.

8. The tire for an automatic two-wheeled vehicle according to claim 1 or 2, wherein the rubber layer is composed of at least one rubber sheet.

9. The tire for an automatic two-wheeled vehicle according to claim 1 or 2, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The distance between the inner side belt ply and the outer side belt ply at the position where the rubber layer is arranged is 0.5 mm to 3.0 mm.

10. The tire for an automatic two-wheeled vehicle according to claim 8, wherein, The rubber layer has a complex modulus at 70°C of 500 kPa or more.

Images